A tracing framework is used to understand the behavior of complex computer systems. Tracing performed using the tracing framework involves recording data from a location or relating to an occurrence in the software of the computer system. In a tracing framework that offers comprehensive coverage, the framework provides a mechanism to allow events not to be traced or the user may be flooded with unwanted data.
Tracing frameworks use predicates to limit the events traced by only tracing data if a certain condition is found to be true. Predicates are a useful mechanism when the user knows which events are interesting. For example, if the user is only interested in an activity associated with a certain process or a certain file descriptor, the user can define a predicate that obtains knowledge about only that particular process or file descriptor.
Additionally, in a tracing framework that gives a high degree of latitude, evaluating a predicate may have a non-zero cost. Further, if a large number of predicates require evaluation, the cost of evaluating the predicates becomes substantial.